Ground anchor

ABSTRACT

Ground anchor designed to be screwed into the ground, comprising a shaft ( 3 ), whose upper end ( 8   a ) is provided with a bearing part ( 8 ) that can be placed on the ground, and a manipulation device ( 9 ). Said anchor has several screw-thread blades ( 5, 6, 7 ) consisting of a flat material, which spiral around the shaft ( 3 ), are arranged along the shaft ( 3 ) at a distance from one another in an offset manner, and respectively consist of a screw thread with upper and lower blade ends ( 11, 12 ). The length of the thread of the individual blades ( 5, 6, 7 ) slightly exceeds 360°, so that the perimeter of the blade ends ( 11, 12 ) overlaps, forming a cutting gap ( 11   a ) that is delimited by a plane on its upper and lower borders. The exterior diameter of the blades ( 5, 6, 7 ) decreases from blade to blade from the bearing part ( 8 ) down towards the lower end of the shaft. The shaft tip ( 22 ) is configured in the same manner as a wood-screw shaft, with a conical core ( 23 ) that tapers towards the tip of the free lower shaft end ( 25 ) and a continuous thread ( 27 ) spiralling around said core ( 23 ).

[0001] The invention relates to a ground anchor for screwing into the ground comprising a shaft whose upper end is provided with a bearing part that can be placed on the ground, and a manipulation device, comprising a plurality of screw-thread blades consisting of a flat material, which spiral around the shaft, which are arranged along the shaft at a distance from one another in an offset manner, and which respectively consist of a screw thread with lower and upper blade ends, with the thread length of the individual blades slightly exceeding 360° so that the blade ends overlap in the circumferential direction forming a cutting gap that is delimited by a plane on its upper and lower borders, with the outer diameter of the blades decreasing from blade to blade from the bearing part towards the lower shaft end.

[0002] Such a ground anchor is known from DE 44 24 339 C2. This ground anchor has proved its worth in practice. It is stable even in sandy soil.

[0003] The object of the invention is to further increase the stability of this anchor and to modify it so that it can be twisted into the earth more easily.

[0004] This object is solved according to the invention by shaping the tip of the shaft in the fashion of a wood screw shaft with a conically tapering core at the free lower end of the shaft and a continuous thread winding spiralling around the core.

[0005] A ground anchor with this shaft tip has greater stability once it has been twisted into the ground. But, importantly, it can be twisted into the ground more easily. This is because the wood-screw-shaped shaft tip pulls downwards the shaft with the blades arranged at a distance and the blades arranged at a distance are thus subjected to a downward force during screwing or twisting into the ground. Thus, they cut into the soil being pulled downwards.

[0006] According to a further development of the invention, it is provided that the helix angle of the screw thread in the region of the core of the shaft tip is greater than the helix angle of the blades arranged at a distance. With this increased helix angle, the shaft tip exerts a greater force on the ground anchor when being screwed in.

[0007] According to a further development of the invention, it is provided that the screw thread in the region of the shaft tip has a cross-sectional profile tapered in a wedge-shaped fashion from the core outwards. The wedge-shaped tapered cross-sectional profile makes the shaft tip into a kind of drill that digs its way into the ground.

[0008] According to a further development of the invention, it is provided that the height of the screw thread remains substantially the same except for the run-out at the open end of the shaft tip

[0009] According to a further development of the invention, it is provided that the shaft tip is exactly centred on the shaft. This exact centring is important for easy, clean insertion into the soil.

[0010] According to a further development of the invention, it is provided that the ball socket in the movable head can be stopped in a set head position by means of a clamping screw. This can thus prevent the movable head from being accidentally or unintentionally displaced from its intended position.

[0011] According to a further development of the invention, it is provided that that the clamping screw is a headless screw.

[0012] According to a further development of the invention, it is provided that the lowest of the blades arranged at a distance has a greater bend at the lower edge than the other blades arranged at a distance. This greater bend of the lower edge facilitates screwing.

[0013] The ground anchor loosens the soil as it is screwed therein. It was assumed that the anchor would therefore be less secure. However, this is wrong.

[0014] This loosening specifically increases the stability and thus the load-bearing capacity.

[0015] The dimensions of the ground anchor are adapted to the conditions of use. It is suitable from the smallest size, such as for anchoring tents, to the largest used in securing foundations for construction.

[0016] The invention is explained in greater detail with reference to the drawings.

[0017] The drawing shows a ground anchor with a shaft whose upper end is provided with a bearing part and a manipulation device. The screw-thread blades are arranged at a distance along the shaft. The shaft tip at the bottom that penetrates into the soil is shaped like a wood screw shaft. It is tapered towards the open end and is provided with a continuous thread constructed as a threaded rib at the outer wall whose helix angle is greater than that of the screw-thread blades arranged at a distance.

[0018] The ground anchor 1 shown in the drawing consists of a shaft 3 whose upper end is provided with a bearing part 8. The bearing part 8 consists of a plate 8 a and a collar 8 b that extends downwards, fully enclosed, from the edge of the plate 8 a. The diameter of the bearing part 8 is, for example, 4 cm greater than that of the screw-thread blades 5, 6, and 7, which are arranged along the shaft 3 at a distance from one another and are described in greater detail below. The difference in diameter can also be greater than 4 cm. A fixing device 9 is attached to the plate 8 a, preferably welded on. The shaft 3 extends through the plate 8 a into the fixing device 9.

[0019] The blades 5, 6 and 7 on the shaft 3 consist of flat sheet material. They wind individually around the shaft 3 and have a winding length somewhat longer than the full winding path of 360°. In this way, a cutting gap 11 a is obtained for each blade 5, 6, 7 between the upper blade end 11 and the lower blade end 12 in the overlapping range. The overlap can be between 25 and 55 degrees. Overlaps of 35 to 45 degrees are preferred. The blades 5,6,7 run in planes radial to the shaft 3.

[0020] While the blades 5,6,7 preferably run out in the blade plane 11 c at their upper edges 11 b, the lower edges 12 b are bent downwards. The bending at the lower edge 12 b of the lowest blade 7 is clearly greater here than that of the other blades 5, 6. The bending of the edges 12 b has a positive influence an the screwing effect of the ground anchor. The slopes of the blades 5,6,7 are adapted to each other. The outer diameter of the blades 5,6,7 decreases uniformly downwards from the bearing part 8 to the shaft tip 10. The highest blade 5 has a distance from the bearing part 8 that can be less than the distance of the blades 5,6,7 one from the other.

[0021] The manipulation device 9 has a movable head 13 that is secured by welding to the plate 8, for example. This movable head 13 has a square or hexagonal external shape for attachment of a turning tool not shown. The ground anchor can be screwed into the ground with such a tool. The movable head 13 has a ball-socket-shaped cavity 13 a. Inserted into this cavity 13 a is a ball socket 14 a to which a pipe 14 can, for example, be welded. The ball socket 14 a with the pipe 14 can be adjusted into the desired swivel position within certain limits. In order that it can swivel, the ball socket 14 a is provided with an opening 14 b at the bottom. A clamp socket 15 is inserted into the ball socket 14 a. The ball socket 14 a is fixedly connected to the clamp socket 15 in the desired position by means of the adjusting screw 17, which is screwed through the clamping socket 15 and the ball socket 14 a into a screw tap 13 b of movable head 13. The opening 14 b in the ball socket 14 a must be sufficiently large for this purpose. A fence post 18 can be connected to the pipe 14, for example. Fastening screws 19 can connect the pipes 14 and 18. In the movable head 13 there is provided a headless screw 20 that is turned with the pipe 14 after the ball socket 14 a has been aligned and thus presses against the ball socket 14 a; the headless screw digs into the socket, thus holding it in the desired swivel position.

[0022] A special shaft tip 22 is provided at the lower end 21 of the shaft 3 which facilitates screwing the ground anchor into the soil. The shaft tip 22 is constructed in the fashion of the shaft of a wood screw. The core 23 of the shaft tip 22 is preferably welded to the end 21 of the shaft 3. Naturally, other suitable fastenings are feasible and possible. The core 23 runs from the fastening position 24 to its open end 25, tapering down to the anchor tip 26. A continuous screw thread 27 winds around the core 23.

[0023] The helix angle of the screw thread 27 in the area of the core 23 of the shaft tip 22 is greater than the helix angle of the blades 5,6,7 arranged at a distance. The shaft tip 22 thus provides for a better drawing-in effect.

[0024] The screw thread 27 has a wedge-shaped tapered cross-sectional profile from the core 23 outwards in the area of the shaft tip 22. The height of the screw thread 27 preferably remains substantially the same except for the run-out 28 at the open end 25 of the shaft tip 22.

[0025] It is important that the shaft tip 22 is exactly centred on the shaft 3. Exact centring prevents problems during screwing and is crucial for straight screwing.

[0026] It is favourable if the circumferential edges of the blades are clearly circular. The force required for twisting is thus small. The ground anchor is made of steel and preferably galvanized. Other materials such as stainless steel are suitable for large anchors for pipe supports or the foundations of buildings or other types of structures. Plastic can be used for light fixings such as guy ropes. 

1. A ground anchor for screwing into the ground, which is divided into a bearing part (8), a shaft (3) and a shaft end (21), wherein the ground anchor has in the region of its upper end (8 a) a bearing part (8) that can be placed on the ground (8) and a manipulation device (9), comprising a plurality of screw-thread blades (5, 6, 7) consisting of a flat material, which spiral around the shaft (3), which are arranged along the shaft (3) at a distance from one another in an offset manner, and which respectively consist of a screw thread with upper and lower blade ends (11, 12), wherein the thread length of the individual blades (5, 6, 7) slightly exceeds 360° so that the blade ends (11, 12) overlap in the circumferential direction, forming a cutting gap (11 a) that is delimited by a plane on its upper and lower borders, with the outer diameter of the blades (5, 6, 7) decreasing from blade to blade from the bearing part (8) down towards the lower shaft end (21), and a shaft end (21) with shaft tip (22), characterised in that the shaft tip (22) is fitted with a conically tapering core (23) at the free lower shaft end (25) and the shaft tip (22) is constructed in the fashion of a wood screw shaft with a continuous screw thread (27) spiralling around the conically tapering core (23), wherein the screw thread (27) has a wedge-shaped cross-sectional profile from the core (23) outwards.
 2. The ground anchor according to claim 1, characterised in that the helix angle of the screw thread (27) in the region of the core (23) of the shaft tip (22) is larger than the helix angle of the blades (5, 6, 7) arranged at an angle.
 3. The ground anchor according to any one of claims 1 and/or 2, characterised in that the height of the screw thread (27) remains substantially the same except for the run-out area at the free end (25) of the shaft tip (22).
 4. The ground anchor according to any one or more of the preceding claims, characterised in that the shaft tip (22) is arranged precisely centred on the shaft (3).
 5. The ground anchor according to any one or more of the preceding claims, characterised in that a ball socket (14 a) in the movable head (13) of the manipulation device (9) can be stopped in a set head position by means of a clamping screw (20).
 6. The ground anchor according to any one or more of the preceding claims, characterised in that the clamping screw (20) is a headless screw.
 7. The ground anchor according to any one or more of the preceding claims, characterised in that the lowest (7) of the blades (5, 6, 7) arranged at a distance has a greater bend at the lower edge (12 b) compared with the other blades (5, 6, 7) arranged at a distance. 